In display technology, a pixel unit in a display apparatus often includes a thin film transistor (TFT). The TFTs can drive the pixel units to display images.
A TFT can be an a-Si (amorphous silicon) TFT. An a-Si TFT often includes: a substrate, and a gate electrode, a gate insulating layer, an active layer, and a source-drain layer formed on the substrate. The active layer includes an a-Si layer, made from a-Si material. The source-drain layer includes a source electrode and a drain electrode, and each has a contact with the a-Si layer. The drain electrode also has a contact with the pixel electrode in the pixel unit. The gate electrode can control the on and off states of the TFT. When the TFT is switched on, current may flow from the source electrode, through the a-Si layer and the drain layer, to the pixel electrode, to charge a pixel electrode.
The conventional technology has at least the following issues: because the source electrode and the drain electrode each contacts the a-Si layer, when charging the pixel electrode, the current from the source electrode of the TFT needs to flow through the a-Si layer to reach the drain electrode. The electron mobility of the a-Si is relatively low. As a result, the on-state current of the a-Si TFT is relatively low, and the charging rate is undesirably low.